The present invention relates to methods of producing lignin peroxidase and its use in skin and hair lightening.
Melanin
The color of human skin and hair is governed by the quantity, quality, and distribution of melanin, a pigment which is also present in plants and microorganisms.
The synthesis of melanin initiates from the precursor L-tyrosine which is transformed into a second precursor dopaquinone via the action of tyrosinase. In the biosynthesis of mammalian melanin this intermediate may be polymerized via two major pathways (FIG. 1). Intramolecular nucleophilic addition of the amino group gives rise to the indole derivative leucodopachrome which, following polymerization, yields the dark brown to black pigment eumelanin. In the presence of thiol compounds thioesther derivatives of dopa are formed; the reaction with cysteine yields cysteinyldopa, which following further oxidation and polymerization yields the yellow to reddish brown pigment phaeomelanin. Consequently, eumelanin is mainly composed of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) units, whereas phaeomelanin mainly contains benzothiazine units (Alaluf et al., 2001). The availability and mutual ratio of these two pigments influences the chemical composition of the polymeric pigment.
Synthesis of melanin takes place in granules, which are referred to as melanosomes (Cooksey et al., 1997) which are present in melanocyte cells present in the epidermal basal layer; synthesis of melanin in these cells is induced by ultraviolet (UV) light. Following synthesis, melanin migrates to epidermal cells and is dispersed therein, where melanin is decolored following dermal metabolism and then scaled off in the form of dirt at the time of skin renewal. Melanin has a clinical importance since it protects the skin from adverse effects caused by UV light. However, high levels of melanin can result in unwanted skin and hair darkening, while the heterogeneous distribution thereof can lead to chloasma and freckling which can be aesthetically displeasing.
Lightening Products
Skin lightening products have become increasingly popular in the past few years. The main purpose of skin lightening products is to lighten or whiten the skin or to treat pigmentation disorders such as chloasma, freckles, pregnancy marks and age spots. Several types of skin lightening products are presently available.
Products based on the degeneration and death of pigment cells typically include harsh chemicals, such as hydroquinone, 4-isopropylcatechol, and hydroquinone monobenzyl ether, that promote skin whitening and skin lightening or fade out skin pigmentation. Such products are typically inefficient and may be harmful to the skin since a continuous external application of these products can lead to permanent leucoderma and side effects such as dyschromatosis and rash.
Other lightening products are based on the inhibition of tyrosinase, the enzyme that transforms the precursor L-tyrosine into a second precursor dopaquinone. This group of products includes Arbutin, a glucose hydroquinone compound which is capable of inhibiting tyrosinase by chelating copper ions thereby suppressing the tautomerization from Dopachrome to DHICA.
Melanostat is another lightening product that acts through tyrosinase. Melanostat is a synthetic peptide that functions in deactivating melanogenesis in melanocytes.
Several antioxidant compounds that can inhibit the production of melanin are also utilized in lightening products. Since the synthesis of melanin involves an oxidation reaction, blocking the oxidation at various points from tyrosine/DOPA to melanin ultimately inhibits the synthesis of melanin.
One antioxidant which is utilized to block melanin synthesis is L-Ascorbic (Vitamin C) which acts as a reducing agent on melanin intermediates and blocks oxidative reactions; other antioxidants utilized by lightening products include bioflavonoids which are typically extracted from mulberry or licorice.
Hair lightening products act on the melanin inside the hair cortex. There are several chemicals that can lighten hair, among these are included hydrochloric acid, sodium hypochlorite and hydrogen peroxide.
The most commonly used chemical for lightening hair is hydrogen peroxide. To maintain desired effectiveness, solutions of hydrogen peroxide must be stabilized using compounds such as acetanilide, dilute acids, colloidal silica, p-hydroxybenzoates, oxyquinoline sulfate, phenacetin, and tin compounds (sodium stannate, stannic hydroxide, stannous octoate). Before hair is lightened, ammonia is added to the hydrogen peroxide solution to enhance penetration of hydrogen peroxide through the cuticle, the outer layer of the hair, and to thus accelerate the oxidation reaction.
While reducing the present invention to practice, the present inventors have uncovered that Lignin peroxidase isoenzyme H1 can oxidize melanin in vitro and can further lighten skin and hair in vivo.
Thus, the present invention provides cosmetic compositions and methods which are highly suitable for skin and hair lightening.